Cancer is a term used to describe a group of malignancies that all share the common trait of developing when cells in a part of the body begin to grow out of control. Most cancers form as tumors, but can also manifest in the blood and circulate through other tissues where they grow. Cancer malignancies are most commonly treated with a combination of surgery, chemotherapy, and/or radiation therapy. The type of treatment used to treat a specific cancer depends upon several factors including the type of cancer malignancy and the stage during which it was diagnosed.
Imatinib has the following formula:
and its salts, particularly the imatinib mesylate, are one of the more commonly used chemotherapeutic agents used for the treatment of Philadelphia chromosome positive chronic myeloid leukemia in blast phase, accelerated phase or chronic phase. This compound has been associated with debilitating side effects such as hepatotoxicity and hematologic toxicity, edema, nausea, vomiting, diarrhea, muscle cramps, musculoskeletal pain and rash. By monitoring the levels of imatinib, its salts or its pharmacologically active metabolites in the body and adjusting the dose, these side effects can be better controlled and limited in patients (Gleevec package insert, Novartis Pharmaceuticals Corporation, East Hanover, N.J., July 2004).
The preferred salt of imatinib is imatinib mesylate which has the formula:

Since imatinib has been associated with debilitating side effects, by monitoring the levels of this chemotherapeutic agent in the body and adjusting the dose, these side effects can be better controlled and limited in patients.
When administering imatinib or its salts to patients, there is often high variable relationship between the dose of imatinib or its salt, and the resulting serum drug concentration of these chemotherapeutic agents or their chemotherapeutically active metabolites, that affects the degree of clinical effectiveness and toxicity. The degree of intra- and inter-individual pharmacokinetic variability of imatinib and its salts has been reported to be four fold (See Gleevec package insert, Novartis Pharmaceuticals Corporation, East Hanover, N.J., July 2004, Pindolia et.al. Pharmacotherapy, 22:1249-1265, 2002) and is impacted by many factors, including:                Organ function        Genetic regulation        Disease state        Age        Drug-drug interaction        Time of drug ingestion        Compliance        
As a result of this variability, equal doses of the same drug in different individuals can result in dramatically different clinical outcomes. The effectiveness of the same imatinib or its salts dosage varies significantly based upon individual drug clearance and the ultimate serum drug concentration in the patient. Therapeutic drug management would provide the clinician with insight on patient variation in drug administration. With therapeutic drug management, drug dosages could be individualized to the patient, and the chances of effectively treating the cancer without the unwanted side effects would be much higher.
In addition, therapeutic drug management of imatinib or its salts would serve as an excellent tool to ensure compliance in administering chemotherapy with the actual prescribed dosage and achievement of the effective serum concentration levels. Routine therapeutic drug management of imatinib or its salts would require the availability of simple automated tests adaptable to general laboratory equipment.
The use of liquid chromatography (LC)-tandem mass spectroscometry to determine the concentration of imatinib, imatinib salts or their chemotherapeutic metabolites in human blood and plasma has been described (Guetens, J Pharm Biomed Anal., 33(5):879-89 2003; Bakhtiar, J Chromatrography B, 768(2):325-340, 2002; Titier, Ther. Drug. Monit., (27)5:634-640, 2005). A LC method to determine the purity of imatinib, imatinib salts or their chemotherapeutic metabolites (Vivekanand, J Pharm Biomed Anal., 28(6):1183-94, 2002) has also been developed but was not used to determine levels in biological fluids. These methods are labor intensive, use expensive equipment and are not amenable to routine clinical laboratory use.
Assay conditions have been described to monitor the activity of protein tyrosine kinases using ATP, where the phosphorous is labeled with a P32 radioactive isotope in a variety of formats including scintillation proximity, solid phase, filtration and radio-autographic assays (Evans et.al., J Biochem Biophys Methods, 50:151-161, 2002; Park et.al., Anal Biochem., 269:94-104, 1999; Witt et.al., Anal Biochem., 66:253-258, 1975; Braunwalder et. al., Anal Biochem., 234:23-26, 1996; Schaefer et. al., Anal Biochem., 261:100-112, 1998). Non-radio-isotopic assays have also been developed using enzyme-linked immunosorbent (ELISA), fluorometric, fluorescent polarization formats (Yamato et. al., Anal Biochem., 315:256-261, 2003; Angles et. al., Anal Biochem., 236: 49-55, 1996; Braunwalder et. al., Anal Biochem., 238:159-164, 1996; Seethala et. al. Anal Biochem., 255:257-262, 1998; Barker, Biochem., 34(45):14843-51, 1995).
These methods were developed to either screen for protein tyrosine kinase activity in biological extracts or for screening potential new inhibitors of the tyrosine kinases. In addition these methods are not amenable for use on routine clinical analyzers. Furthermore, they do not provide a method to directly quantitate imatinib, its salts or their thereapeutically active metabolites, in the patients plasma or serum for the purpose of therapeutic drug monitoring.